The present invention generally relates to systems and methods for regulating fluid flow, particularly within a subterranean formation, and, more specifically, to rotational motion-inducing variable flow resistance systems having a sidewall fluid outlet that allows the variable flow resistance systems to be connected in series fluid communication with one another.
It can often be beneficial to regulate the flow of formation fluids within a wellbore penetrating a subterranean formation. A variety of reasons or purposes can necessitate such regulation including, for example, prevention of water and/or gas coning, minimizing water and/or gas production, minimizing sand production, maximizing oil production, balancing production from various subterranean zones, equalizing pressure among various subterranean zones, and/or the like.
Likewise, it can also be beneficial to regulate the flow of injection fluids such as, for example, water, steam or gas, within a wellbore penetrating a subterranean formation. Regulation of the flow of injection fluids can be particularly useful, for example, to control the distribution of the injection fluid within various subterranean zones and/or to prevent the introduction of injection fluid into currently producing zones.
A number of different types of flow resistance systems have been developed in order to meet the foregoing needs. Many of these flow resistance systems are variable flow resistance systems that can restrict the passage of some fluids more than others based upon one or more physical property differences between the fluids. Illustrative physical properties of a fluid that can determine its rate of passage through a variable flow resistance system can include, for example, viscosity, velocity and density. Depending on the type, composition and physical properties of a fluid or fluid mixture whose passage is to be restricted, variable flow resistance systems can be configured such that higher ratios of a desired fluid to an undesired fluid can flow through a flow pathway containing the variable flow resistance system.
Rotational motion can be particularly effective for variably restricting fluid flow within a variable flow resistance system. In variable flow resistance systems capable of inducing rotational motion, a fluid composition most often enters a chamber within the variable flow resistance system in such a way that an undesired component of the fluid composition undergoes greater rotational motion than does a desired component of the fluid composition. As a result, the undesired component traverses a longer flow pathway than does the desired component, and the undesired component's residence time within the variable flow resistance system can be increased. Most often, the variable flow resistance system is configured such that fluid exiting the variable flow resistance system is discharged through a hole in the bottom of the chamber. Although such an arrangement of the exit hole can be particularly effective for inducing vortex-like rotational motion within a fluid, it significantly complicates the coupling of multiple chambers to one another in linear series.
Multiple chambers having a bottom exit hole can be series connected to form an operable variable flow resistance system, but the resulting arrangement of the chambers can be inefficient in terms of space utilization. For example, FIGS. 1A-1C show side view schematics of several possible arrangements of multiple chambers having a bottom exit hole that are in series connection with one another. As shown in FIGS. 1A and 1B, bottom exit hole 9 of chamber 5 within variable flow resistance systems 1 and 3 can particularly lend itself to vertical (FIG. 1A) or stepped-vertical (FIG. 1B) arrangements of the chambers. In confined locales, such as, for example, within a wellbore, such arrangements can prove problematic in terms of available space utilization. As shown in FIG. 1C, a substantially horizontal arrangement of chambers having a bottom exit hole within variable flow resistance system 4 is possible, at least in principle. However, the substantially horizontal arrangement of chambers shown in FIG. 1C can also prove problematic by requiring a vertical movement of fluid during transit between adjacent chambers.